The discussion below is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter. WO2006/091093 discloses an ultrasound treatment head comprising at least one active element for converting an electric signal into ultrasound, a vacuum cup having an upper part and a lower part, wherein the active element is mounted in the upper part and the vacuum cup provides a vacuum chamber with a holding space for a gel pad. The treatment head can be fixed to the part of the patient's body to be treated in a relatively simple manner by using an underpressure generated in the vacuum cup by a vacuum pump. The vacuum pump can be part of the apparatus for treating a patient with ultrasound. In this manner the person in attendance does not need to stay with the patient during the treatment. The acoustic coupling between the active element and the part of the body that is to be treated depends on the fixation of the treatment head on the body part and the effectiveness of the coupling medium, generally water, provided by the gel pad. To this end the percentage of the coupling medium in the gel pad should be high. However, a high percentage of coupling medium results in a very slippery gel pad surface, so that in the known treatment head it is very difficult if not impossible to keep the gel pad located between the active element and the body part of the patient during a treatment.